And if Groupon went in the red by $414 million last year, what about its closest competitor, D.C.-based LivingSocial, which has similarly shoveled funds into acquiring customers, making acquisitions and broadening its reach over the same period?

Tim O’Shaughnessy, co-founder and chief executive of District-based LivingSocial, has said the firm expects to take in $1 billion in revenue this year. The size (or existence) of its earnings are a bit more murky.

One of its biggest new investors has been quoted as saying LivingSocial is already making profits. The company has been otherwise mum on the issue.

“We have seen high growth companies and LivingSocial is just growing at an incredible rate and they are profitable," said Todd Chaffee, a general partner with Institutional Venture Partners, told Reuters in April.

But the magnitude of Groupon’s loss raises the question of whether a rapidly expanding daily deal site can be profitable at the same time – even while its revenues are skyrocketing. Groupon booked $713 million in revenues last year, and $644 million in revenues in the first three months of 2011. Its first quarter net loss, however, stood at $113 million.

That red ink might be something investors will have to tolerate for some time, Groupon CEO Andrew Mason suggested in a letter accompanying the IPO filing.

“In the past, we've made investments in growth that turned a healthy forecasted quarterly profit into a sizable loss,” Mason wrote. “When we see opportunities to invest in long-term growth, expect that we will pursue them regardless of certain short-term consequences.”